☯ TCM Properties
Nourishes the Blood an Jing; Stimulates digestion, stimulates the Gall Bladder, removes accumulation, resolves Phlegm-Dampness relieves fullness and kills parasites; Promotes urination, resolves toxicity, clears the skin and softens hardness; Resolves Phlegm, promotes expectoration, opens the nasal passages and stops cough; Promotes lactation
Traditional Chinese Uses
Xi Yang Cai ("Western ocean vegetable") is watercress, Nasturtium officinale, valued in Chinese medicine chiefly as a moistening, cooling food-herb for the Lung. It is used to resolve Phlegm, clear Lung Heat and stop cough, addressing dry cough, sticky or hard-to-expectorate phlegm, sore or dry throat and hoarseness — commonly simmered into soups for autumn dryness patterns. It also promotes urination and clears Heat to relieve mild Dampness, and is used to stimulate digestion and support convalescence.
The record's tcm_functions list a broad, somewhat encyclopedic range (blood nourishing, resolving toxicity, promoting lactation); in mainstream Chinese dietary therapy its best-documented use is moistening the Lung and transforming Phlegm to stop cough. Generally regarded as a safe culinary herb.
Western Herbalism Properties
Botanical Description
Nasturtium officinale W.T.Aiton (Brassicaceae), watercress, called Xi Yang Cai ("Western ocean vegetable") in Chinese for its European origin, is a perennial aquatic or semi-aquatic herb with hollow, succulent, creeping or floating stems 20-90 cm long rooting at the lower nodes in slow-moving freshwater streams and springs. The leaves are alternate, pinnately compound with 3-9 ovate to oblong leaflets, the terminal leaflet largest, all dark glossy green, slightly fleshy, and pungent. Small four-petalled white flowers, 4-6 mm across, are borne in terminal racemes that elongate in fruit, followed by slender curved siliques 1-2 cm long containing two rows of small reddish seeds. Native to Europe and West Asia and now naturalised worldwide, watercress is widely cultivated as a salad green in China. In southern Chinese folk and TCM-adjacent practice, the fresh whole herb is used to clear lung heat, moisten dryness, cool blood, promote urination, and relieve cough; it is also valued nutritionally for vitamin C and glucosinolates.
Active Constituents
Gluconasturtiin
Aromatic glucosinolateConcentration: Predominant glucosinolate of watercress
The storage precursor that, on tissue damage and myrosinase hydrolysis, releases phenethyl isothiocyanate. It is the source of watercress's chemopreventive activity and pungent flavour.
Phenethyl isothiocyanate (PEITC)
IsothiocyanateConcentration: Formed on hydrolysis of gluconasturtiin
The key bioactive metabolite. It inhibits phase I carcinogen-activating enzymes (including CYP2E1) while inducing phase II detoxifying enzymes, and shows anti-inflammatory, pro-apoptotic and anticancer activity in numerous experimental models.
Vitamin K1 (phylloquinone)
Fat-soluble vitamin (naphthoquinone)Concentration: High (a rich dietary source)
Essential cofactor for hepatic clotting-factor synthesis; the high content is the basis of watercress's interaction with vitamin-K-antagonist anticoagulants.
Vitamin C (ascorbic acid)
Water-soluble vitaminConcentration: High
Antioxidant and cofactor supporting the plant's overall free-radical-scavenging and immune-supportive properties.
Carotenoids (beta-carotene, lutein, zeaxanthin)
CarotenoidsConcentration: High
Provitamin-A and antioxidant pigments contributing to eye and skin protection and to the antioxidant activity demonstrated in supplementation trials.
Flavonoids (quercetin, kaempferol and isorhamnetin glycosides)
Flavonol glycosidesConcentration: Major polyphenol fraction
Antioxidant and anti-inflammatory polyphenols that account for much of the measurable radical-scavenging capacity of the aerial parts.
Hydroxycinnamic acids (chlorogenic, ferulic, caffeic acids)
Phenolic acidsConcentration: Variable
Contribute additional antioxidant and anti-inflammatory activity.
⚠ Drug Interactions
Warfarin and other vitamin-K-antagonist anticoagulants
Watercress is rich in vitamin K1, which supplies the cofactor for hepatic synthesis of clotting factors that warfarin suppresses. A large or fluctuating intake can antagonise anticoagulation and lower the INR.
Clinical note: Patients on warfarin should keep vitamin-K (green-vegetable) intake consistent; avoid sudden large increases in watercress consumption.
CYP2E1 substrates (e.g. chlorzoxazone, and CYP2E1-dependent bioactivation of paracetamol/acetaminophen)
Phenethyl isothiocyanate from watercress inhibits CYP2E1. In a controlled human study a single 50 g dose of watercress increased chlorzoxazone AUC by 56% and prolonged its half-life by 53%, confirming clinically relevant CYP2E1 inhibition.
Clinical note: Effect is transient after a single dose but may raise exposure to CYP2E1-cleared drugs; relevant when large amounts are consumed with such medicines.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 9-30g | Daily | — | — | — |
Preparation Methods
Fresh raw herb (salad or juice)
Parts: aerial parts, leaf, stem
Eaten raw or freshly juiced so that intact myrosinase can hydrolyse gluconasturtiin to active phenethyl isothiocyanate. Chewing or crushing the fresh herb maximises isothiocyanate release; this is the form used in the clinical supplementation studies.
Light cooking / soup
Parts: aerial parts
Briefly cooked in soups and broths in Cantonese folk practice for clearing heat and moistening the Lung. Prolonged heat denatures myrosinase and lowers isothiocyanate yield, so gentle, short cooking is preferred to preserve activity.
Clinical Studies
Watercress supplementation in diet reduces lymphocyte DNA damage and alters blood antioxidant status in healthy adults
Sixty adults (30 smokers, 30 nonsmokers) ate 85 g raw watercress daily for 8 weeks. Supplementation reduced basal lymphocyte DNA damage by 17% and oxidative purine DNA damage by 23.9%, and raised plasma carotenoids, with larger benefits in smokers.
Inhibition of chlorzoxazone metabolism, a clinical probe for CYP2E1, by a single ingestion of watercress
Ten healthy volunteers took the CYP2E1 probe chlorzoxazone before and after a single 50 g watercress homogenate. Watercress increased chlorzoxazone AUC by 56% and prolonged half-life by 53%, demonstrating in vivo CYP2E1 inhibition.
Immunomodulating Effect of the Consumption of Watercress (Nasturtium officinale) on Exercise-Induced Inflammation in Humans
Nineteen healthy subjects consumed 85 g fresh watercress or a control meal before high-intensity exercise. Watercress produced a mild acute pro-inflammatory cytokine rise followed by stronger anti-inflammatory down-regulation of IL-6 and TNF-α during recovery.
Historical Texts
Dioscorides, De Materia Medica
1st century CEZhonghua Bencao (Encyclopedia of Chinese Materia Medica)
Modern (1999)References
- Klimek-Szczykutowicz M, Szopa A, Ekiert H. Nasturtium officinale (Watercress): phytochemistry, pharmacology and applications . Frontiers in Plant Science (glucosinolate/isothiocyanate profiling of watercress) (2022) [DOI]
- Chen L, et al.. Watercress monograph - uses, interactions and precautions . Natural Medicines / WebMD ingredient monograph (2023) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
📝 Notes
Public notes from the community and your own private notes on Xi Yang Cai.
No notes yet.